Impedance-Based Characterization and Experimental Stability Analysis of Grid-Forming Converters with Virtual Admittance Control

Grid-connected power converters increasingly utilize grid-forming (GFM) control to enhance system stability and support a high penetration of power electronics. However, GFM converters can introduce instabilities in strong grids and interact with neighboring converters. Suitable modeling approaches, such as impedance-based methods, can help assess and mitigate these stability issues. This paper develops a comprehensive impedance model for GFM converters based on virtual admittance control, which has recently attracted significant research interest. The impact of key control parameters on impedance characteristics is investigated. The impedance model is validated through experimental impedance measurements. Insights derived from the model are further used to assess and mitigate converter interactions in laboratory experiments.